Both of them belong to online UPS(Double Conversion UPS), and their core commonality is: regardless of whether the power grid is normal or not, the load is always powered by the inverter of UPS (grid power → rectification → DC → inverter → AC), which realizes "zero switching" power supply, ensures that the load is not affected by power grid fluctuation and power outage, and the power supply stability far exceeds that of backup/interactive UPS.
The core of the difference lies in the topological structure of rectifier and inverter and whether they contain power frequency transformer, which directly leads to the difference in working principle, performance and applicable scenarios, especially affecting the selection logic of portable Power Station when it is adapted to high-power household appliances (such as refrigerators and air conditioners) in the African market.
First, the working principle of high frequency online UPS
1. Core structure (no power frequency transformer, high frequency design)
Composition: high frequency rectifier (PFC)→ battery pack → high frequency inverter → static switch (power frequency transformer without bulky).
Key features: High-frequency switching technology (switching frequency is usually 20kHz~100kHz) is adopted for rectification and inverter, which is a mainstream UPS type (suitable for small and medium power loads, and also a common scheme for portable power supply).
2. Detailed workflow
(1) When the power grid is normal (main power supply mode)
Rectification stage: the AC voltage of the power grid (such as 220V/50Hz) is converted into a stable DC voltage (such as 380V DC) by a high-frequency rectifier (with power factor correction PFC), and the battery pack is charged (fully charged).
Advantages of high-frequency rectifier: fast response speed (microsecond level), filtering harmonics and voltage fluctuations in the power grid, and the power factor is close to 1 (reducing power grid loss, meeting the energy-saving requirements of some African countries).
Inversion stage: stable DC is converted into pure sine wave AC voltage by high-frequency inverter (completely synchronized with power grid frequency and phase, with distortion less than 3%), which is directly supplied to loads (such as computers, small household appliances and communication equipment).
The static switch is in the "standby state", which monitors the output of the inverter in real time, and quickly switches to the power grid bypass if the inverter fails (but it does not depend on the bypass when it works normally online).
(2) When the power grid is interrupted/abnormal (battery power supply mode)
At the moment of power failure, the battery pack immediately takes over the power supply: the direct current stored in the battery is directly input into the high-frequency inverter, and the inverter continuously outputs pure sine waves to supply the load.
Switching time: 0ms (zero switching), and the load has no power-off perception (key advantage, suitable for equipment that requires high continuity of power supply, such as medical equipment and communication base stations camping in Africa).
(3) In case of failure/overload (bypass mode)
If the UPS fails internally (such as the inverter is damaged) or the load is overloaded (exceeding the rated power of UPS by 110%~150%), the static switch will switch to the power grid bypass quickly (millisecond level), and the power supply will be directly provided by the power grid, so as to avoid the power failure of the load and protect the internal components of UPS.
3. Key technical features
No power frequency transformer, relying on high-frequency magnetic core materials (such as ferrite) to realize energy conversion, small size and light weight (convenient for portable power supply design).
The inverter has high efficiency (usually 90%~95%) and low energy consumption, which is suitable for long-term online operation.
It has strong adaptability to the power grid, can withstand wide voltage input (such as 110V~300V), and is suitable for the scene of unstable power grid voltage in some African countries.
Second, the working principle of power frequency online UPS
1. Core structure (including power frequency transformer and traditional topology)
Composition: power frequency rectifier → battery pack → power frequency inverter → power frequency isolation transformer → static switch.
Key features: The output end of the inverter is connected in series with a power frequency isolation transformer (50Hz/60Hz, iron core material), which is large in size and heavy (similar to a large transformer) and is mainly used in high-power and heavy-load scenes.
2. Detailed workflow
(1) When the power grid is normal (main power supply mode)
Rectification stage: AC voltage of power grid is converted into DC voltage by power frequency rectifier (usually SCR rectifier), which charges the battery and provides DC input for inverter.
Characteristics of power frequency rectifier: simple structure and strong impact resistance, but slow response speed (millisecond level) and low power factor (usually about 0.8, additional reactive power compensation device is required).
Inversion stage: DC is converted into sine wave AC by power frequency inverter, and then voltage regulation (for example, 380V output by inverter is converted into 220V) and electrical isolation (to avoid power grid interference and protect load safety) are carried out by power frequency isolation transformer.
The isolated pure alternating current is supplied to the load, and the static switch monitors the output of the inverter for standby switching.
(2) When the power grid is interrupted/abnormal (battery power supply mode)
Consistent with high-frequency UPS logic: the battery directly supplies power to the power frequency inverter, and the alternating current output by the inverter is supplied to the load after passing through the isolation transformer, and the switching time is 0 ms..
Advantages: The electromagnetic isolation function of the power frequency transformer can effectively suppress the interference such as surge and lightning stroke in the power grid and protect the load more thoroughly (suitable for high-value equipment in thunderstorm areas in Africa).
(3) In case of failure/overload (bypass mode)
Similar to high-frequency UPS, it is switched to power grid bypass, but some power frequency UPS bypasses are also connected in series with power frequency transformers to further improve power supply stability.
3. Key technical features
The core is the power frequency isolation transformer:
Electrical isolation: the load is completely isolated from the power grid, avoiding the interference of power grid harmonics and ground wires, and protecting precision equipment (such as medical instruments and industrial control equipment).
Strong impact resistance: it can withstand the heavy current starting of loads (such as the starting impact of motor loads) and is suitable for driving inductive loads such as air conditioners, refrigerators and water pumps (most household appliances in the African market are inductive loads, so it is necessary to pay attention to the adaptation of starting power).
Strong structure, high reliability and long service life (usually 10-15 years).
