Online double conversion UPS power supply working mode and technical
status. As we all know, the function of online double-conversion UPS power
supply is to ensure uninterrupted power supply to the load, improve the quality
of the power supply, completely isolate various interferences from the mains
power supply and the load, and ensure that stable and reliable AC can be
supplied to the load under any circumstances. power supply. Different UPS
products and UPS power supply systems are used in different applications.
What double conversion UPS power supply?
The double-conversion UPS power supply circuit structure without bypass is
composed of a rectifier/charger, an inverter, a battery charger (optional), a
battery switch, etc. The structural components of the power supply circuit of
the double conversion UPS with bypass are basically the same as those of the
double conversion UPS without bypass, but a UPS switch module is added for the
UPS to convert from normal mode to energy storage mode or vice versa.
Online double conversion UPS power supply requires two power conversions.
That is, the mains AC input power is first converted into DC power by the
rectifier, and then converted into AC power by the inverter. At the same time, a
rectifier/charger or a separate battery charger charges the battery. The input
power AC input of the rectifier and the input power AC input of the charger can
also use the same power supply.
In normal mode, an online double conversion UPS power supply supplies power
to the load from a rectifier/inverter combination.
When the index of the mains AC input power exceeds the predetermined
tolerance limit, the UPS switches to the energy storage mode, that is, the
battery/inverter combination supplies power to the load. The power supply time
interval is the energy storage time of the battery, or supplies power to the
mains input power. Restore to the design tolerance of the UPS and then switch to
normal mode.
When the rectifier/inverter fails, or when the UPS is instantaneously or
continuously overloaded, the UPS will switch to bypass mode, that is, the load
will be temporarily powered by the bypass power supply. To ensure uninterrupted
conversion, the inverter output and AC input 3 must be synchronized.
Additionally, if the input and output voltages are different, a transformer must
be installed in the bypass circuit.
The inverter of a double-conversion UPS must be synchronized with the
bypass power supply to ensure uninterrupted load conversion. There is also
usually a "maintenance bypass" dedicated to maintenance.
Introduction to the working mode of online double conversion UPS power
supply
(1)Normal way
The AC input power is transformed twice by rectification (AC/DC) and
inverter (DC/AC) through the rectifier/charger-inverter combination circuit. The
load is powered by the inverter. Since all the power required by the load After
two conversions, this UPS is called a double conversion UPS power supply.
(2) Energy storage method
When the AC input power voltage exceeds the predetermined tolerance or
fails, the battery is discharged to supply DC power to the inverter, allowing
the inverter to continue running and continuously supply AC power to the
load.
When the AC input power returns to normal, the UPS power supply returns to
normal working mode. If the AC input power supply is outage for a long time, the
UPS will continue to operate in the energy storage mode until the battery's
energy storage is used up. In order to protect the AC input power supply from
long-term power outages, a backup diesel generator set should generally be
configured.
(3)Bypass mode
Double-conversion UPS power supplies generally have static bypass switches,
which can automatically and temporarily transfer the load from the inverter to
the bypass power supply under the following circumstances.
(4) The battery is discharged to the end voltage
In order to ensure uninterrupted load conversion between the inverter and
the bypass power supply, the UPS inverter must be synchronized with the bypass
power supply in order to adopt a first-on-then-off conversion method, that is,
the inverter and the bypass power supply have Connect in parallel for a brief
period, then disconnect one of the power supplies. There is also a circuit
called maintenance bypass. When the UPS needs maintenance, the load can be
manually switched to the bypass power supply in a first-on-then-off manner
through the maintenance bypass.
Current status of online double conversion UPS power supply technology
Major UPS manufacturers in the world are focusing on developing a new
generation of UPS with superior performance. For example, the iTrust series of
large-capacity UPS recently launched by Liebert Company fully considers the
needs of existing customers. It adopts high-frequency rectification technology
for the input and has an input power factor of up to 0.99 or above, input
harmonic current <3%. In addition, both the rectifier and inverter adopt
fully digital control schemes, which adapt to the development requirements of
modern communication technology. The output still uses a traditional output
isolation transformer, which enhances the anti-interference ability of the
system. At the same time, it greatly reduces the probability of damage to the
user load caused by the output DC voltage caused by control failure, effectively
improving the reliability of the system.
In addition, low-cost and high-performance high-frequency machines will
also become the mainstream models in the market over time. This type of UPS
eliminates the need for an output isolation transformer based on the
above-mentioned future mainstream models, greatly saving costs, which is about
60% of the above-mentioned models, making it highly competitive in the market.
The disadvantage is that the current technology is not mature enough and has low
reliability. However, as the technical level improves, the reliability will be
greatly enhanced. It is believed that this type of model will become the new
mainstream model of UPS in the near future.
In terms of heat dissipation technology, most UPS power supplies currently
use radiators for air-cooling, which are expensive and noisy. Especially for
high-power UPS (capacity above 60kVA), the noise problem is particularly
prominent. In order to make breakthroughs in heat dissipation issues, major UPS
manufacturers have invested a lot of financial resources and manpower in
research.
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